Ballistic primer



May 3, 1966 T. ZIMMERMAN BALLISTIC PRIMER Filed July 5l, 1964 United States Patent O 3,249,049 BALLISTIC PRIMER Theodore Zimmerman, West Caldwell, NJ., assignor to the United States of America as represented by the Secretary of the Army Filed July 31, 1964, Ser. No. 386,798

Y 1 Claim. (Cl. 102-46) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates -to ballistic primers and, more particularly, to an artillery primer arrangement for igniting combustible or consumable case ammunition.

As a corollary to the development of combustible case ammunition came the requirement rfor use therewith of a suitable primer or ignition means which of itself was likewise fully combustible, so as to leave the gun cha-mber free from residue after each ballistic cycle. In early attempts to produce a satisfactory primer, ignition delays or misres under operative conditions usually resulted.

One of the objects of the invention is to produce a fully combustible ignition means for associated fully combustible case ammunition.

Another object of the -invention is .to provide a combustible ignition means that eliminates operational delays or malfunc-tions, and that functions substantially instantaneously permitting rapid tiring rates at all temperature extremes.

Other objects, advantages and features will become -apparent from the following description taken in conjunction with the drawing which is a sectional view of an arrangement embodying the principles of the invention.

ln the preferred embodiment of the invention, the primer head holder assembly 11 is of molded combustible material and resin binder construction provided with a rearmost central passage or opening 13 in which the outer cup 12 seats forwardly against the inwardly extending annular ange of a smaller forward communicative opening 14. The forwardmost outer surface of the holder assembly 11 is recessed for reception of one end of a paper tubular container 15 in which the main charge of black powder 16 is loaded. A paper diaphragm or plug 17 closes off the front end of the tube 15 after insertion of the black powder 16 that will provide t-he required energy to ignite the main propellant charge (not shown).

The outer cup 12 is a substantially cylindrical metallic member having an appropriately apertured forward base portion through which passes a lead sheath covered mild detonating fuze (MDF) 20. The fuze 20 has one end secured in its combustible holder 2'1 within base portion of t-he outer cup 12 and its other end extends forwardly a substantial distance into the black powder 16. Abutting the rear portion of the MDF holder 21 is a combustible explosive holder 22 having a tapered recess deiining a rear air space 19 communicatively connected by central passage 23 to an explosive pocket containing pressed pellets of lead azide 25 and pentaerythritol tetra-nitrate (PETN) 26 located adjacent the rear end of the fuze 20. An onion skin paper 24 prevents rearward leakage of consolidated lead azide pellet through passage 23.

A heat sensitive ignition mix 2-8 in-an appropriate container is positioned adjacent and rearward of the explosive holder 22 and .air space 19. A stainless steel bridge wire 30 extends diametrically across the rear surface of the ignition mix and has its end portion 31 bent around the mix periphery and spot welded to suitable portions of the outer cup cylindrical sidewall. A combustible front support element 32 which abuts the bridge wire 30 and rear surface of the ignition mix, is formed with a relal 3,249,049 Patented May 3, 1966 tively large central rear hole 33 communicating with a smaller front opening 34, the intersection of which de- -ines a ilange 35. An inner metallic sleeve 36 of generally cylindrical coniguration has its forward closed base portion 37 spot welded to the central portion of the adjacent bridge wire. Preferably, inwardly directed offset means 8.8 are formed on the sleeve sidewall to make electrical contact with and guide the gun probe portion 43 t-o its primed position as shown and the open and rear portions of the sleeve are bent outwardly in an abutting relation against the flange surfaces 35. The rearward edge of hole 33, preferably, is formed with an annular taper 40 and the rearward end portions 41 of the outer cup 12, when punctured .by gun probe portion 42, are reversely bent inwardly to abut the lateral surfaces of hole 3-3. Lateral passage 39 permits an electrical continuity check of bridge wire 30 during assembly of the primer.

The gun probe includes portions 42 and 43 which a-re electrically insulated from each other by insulator 4'4 and each portion has a common electrical ground 45. A 24- volt storage battery 46 serves Ias a power source when the liring switch 47 is closed to energize a ring circuit through probe portion 43, sleeve 36, bridge wire 30, cup i12 and gun probe portion 42. The electric current flowing through the bridge wire 30 heats it to incandescence and the heat sensitive ignition mix 28 ignites, the front flame of which traverses passages 19, 23 to ignite the pellets of lead azide 25 and PE'TN 26. This causes the mild detonating fuze 20 to detonate, whereupon the main bed of black powder 16 is substantially instantaneously ignited, as well as all of the other parts of the fully combustible primer, including the electrical contacts which are vaporized. Thus, the entire primer is completely consumed in the ballistic cycle of the gun `firing, and when employed with combustible case ammunition leaves a residue free gun chamber after each firing.

It should be noted that until the primer is punctured to obtain electrical continuity across the bridge wire, it is in an electrical short-circuited condition. As an additional safety feature, the metallic cup 12 conducts away any static electrical charge that may build up on the fuze |20, thereby preventing an electrical discharge from the fuze to the explosive pellet means 2S, 216.

Certain modications, alterations or changes may be resorted to without departing from the scope of the invention as dened in the appended claim.

I claim:

A combustible primer for artillery ammunition comprising,

a primer head holder having a central passage therein,

a longitudinally oriented paper tube extending forwardly from one end of said holder,

black powder filling a substantial lengt-h of said tube with a main charge,

a mild detonating fuze embedded a substantial distance into said black powder and having its rear end connected to a fuze holder,

explosive means positioned within an explosive holder and adjacent said fuze rear end,

a heat sensitive ignition mix communicatively connected with said explosive and having a forward portion in abutment with a rear portion of said explosive holder,

a bridge wire extending across the rear surface of said mix,

a support member in abutment with said wire and having a through bore and rearwardly facing counterore,

`an electrically conductive cup member lining a substantial length of said passage and enclosing as a package said fuze and explosive holders, said mix and said support, said cup having a rear central portion susceptible to puncturing and re-positioning as a reverse bend lining the sidewall of said counterbore,

an electrically conductive sleeve lining sa-id bore and engaging a central portion of said wire,

a gun probe having separate projections normally electrically insulated from each other for insertion lthrough said cup susceptible portion into said lined bore and counterbore respectively to thereby establish electrical continuity between said projections, and

an electrical circuit containing an electrical power source, a ring switch, and each of said probe proto heat said mix in the detonation of said black powder.

References Cited by the Examiner UNITED STATES PATENTS BENJAMIN A. BORCHELT, Primary Examiner. jections, for passing current through said bridge wire 15 R- F. STAHL, Assistant Examiner. 

